Method for separating high-purity metal from neodymium iron boron alloy waste

Abstract

The invention relates to the technical field of resource recovery and metallurgy, and discloses a method for separating high-purity metal from neodymium-iron-boron alloy waste, which comprises the following steps: by taking the neodymium-iron-boron alloy waste as an anode and an inert material as a cathode, oxidizing and dissolving Nd, Dy, Pr, Co and Fe into electrolyte by adopting constant-voltage electrolysis, and separating out part of Fe at the cathode to obtain high-purity iron; adding sodium sulfate into the electrolysis tail liquid, adjusting the pH value, and filtering to obtain sodium sulfate double salt precipitate of rare earth and filtrate; h2O2 is added into the filtrate, sodium jarosite is obtained through filtration by adjusting the pH value, NH4HCO3 is added into the iron-removed filtrate to precipitate CoCO3, and the tail liquid can be directly and repeatedly used in the electrolysis process; the rare earth sodium sulfate double salt precipitate is sequentially subjected to hydrochloric acid dissolution, two-step extraction, precipitation and roasting, and Dy, Nd and Pr oxides are obtained respectively. Comprehensive recovery of metal is achieved through the processes of electrolysis, extraction, precipitation, roasting and the like, and the method has the advantages of being simple in process, high in metal purity, low in material consumption and energy consumption, free of pollution and easy to industrialize.

Description

Technical Field

[0001] The invention relates to a method for separating high-purity metals from NdFeB alloy waste, belonging to the technical field of resource recovery and metallurgy. Background Art

[0002] Rare earth permanent magnets are widely used in electric vehicles, wind power generation, aerospace, electronic information and other fields due to their advantages such as high coercivity, high energy density, high magnetic energy level, easy processing and small size. NdFeB permanent magnet materials have strong intrinsic coercivity and magnetic energy product. They are the most widely used type of rare earth permanent magnet materials and occupy more than 94% of the market share in the entire rare earth permanent magnet industry. my country is the world's largest production base and consumer market for NdFeB permanent magnets, supplying more than 90% of the global NdFeB market. The performance of permanent magnets will decline with the increase of usage time, mainly manifested in magnetic attenuation, temperature influence, corrosion, mechanical damage, external magnetic field influence and aging effect. With the increase of service life, NdFeB permanent magnet materials begin to enter the retired market. It is estimated that the supply of retired rare earth permanent magnet materials can reach 27,000-54,000 tons in 2030. The secondary recycling of discarded NdFeB waste can not only reduce the damage caused by mineral development to the environment, but also improve the supply and demand relationship of rare earths to a certain extent. Therefore, achieving green, efficient and recycling utilization of NdFeB permanent magnet waste is of great significance to maintaining my country's status as a major country in rare earth resources, improving the control capacity of the overall industrial chain and realizing a circular economy.

[0003] At present, the recycling technology of NdFeB alloy waste mainly includes pyrometallurgy, hydrometallurgy and electrochemical method. Pyrometallurgy usually includes oxidation method, chlorination method, liquid alloy extraction method, etc. The advantages of this method are short process and relatively friendly to the environment, but the disadvantages are low product purity and difficulty in industrialization. Hydrometallurgy separates rare earth from other elements by controlling the pH value, then obtains single rare earth compounds by extraction, and finally converts them into salts and roasts them to obtain rare earth oxides. The advantages of this method are strong adaptability of raw materials and high purity of rare earth products, but the process is long, the consumption of acid and organic reagents is large, and the discharge of three wastes is high. Compared with the first two methods, the electrochemical method directly uses magnets as anodes for dissolution, avoiding the need for energy-intensive processes such as crushing, grinding and roasting, thereby saving acid consumption, simplifying operations, and helping to reduce energy consumption.

[0004] CN111154980A discloses a method for electrolytic regeneration of NdFeB waste solution. The method first removes the anti-corrosion layer on the surface of the NdFeB waste, then electrolyzes the NdFeB waste with dilute acid or iron salt as electrolyte, recovers iron at the cathode, and then recovers rare earth elements by step-by-step extraction and precipitation. However, the iron element accounts for more than 60% of the NdFeB waste. During the electrolysis process, the anode is prone to Fe 2+ →Fe 3+Side reactions and the passivation reaction of iron lead to slow dissolution of the anode and Fe 3+ It is easy to hydrolyze to form colloids, while reducing the cathode current efficiency. CN118108260A discloses an electrolytic recovery method for NdFeB magnets. The specific principle is to use NdFeB waste as an anode and an inert electrode as an auxiliary electrode to electrolyze the NdFeB waste electrode to produce rare earth element ions and Fe 2+ etc., the auxiliary electrode will be Fe 2+ Oxidation, and then separation of Fe(OH)3 through hydrolysis. Although this method can easily separate iron, Fe(OH)3 colloid is difficult to filter, and the adsorption of rare earth elements leads to the loss of rare earth elements.

[0005] In view of this, it is necessary to design a new, simple, green and efficient separation and recovery technology to improve the metal recovery rate with significant economic and environmental benefits. Summary of the invention

[0006] The present invention aims to provide a method for separating high-purity metals from NdFeB alloy waste, so as to solve the problems of long NdFeB alloy waste recycling cycle, incomplete metal recycling, low metal recycling rate and high pollution in the prior art.

[0007] To achieve the above object, the present invention adopts the following technical solution: a method for separating high-purity metal from NdFeB alloy waste, comprising the following steps:

[0008] S1. Electrolysis: Use NdFeB alloy scrap as anode and inert material as cathode, add electrolyte, pH buffer, Fe 2+ The complexing agent is used to perform constant voltage electrolysis under acidic conditions to obtain electrolytic tail liquid and cathode iron;

[0009] S2, double salt precipitation: adding sodium sulfate to the electrolytic tail liquid, adjusting the pH value of the solution to make the solution acidic, filtering to obtain sodium sulfate double salt precipitate and filtrate of rare earth;

[0010] S3, separation of Fe and Co: H2O2 is added to the filtrate of step S2, the pH value of the solution is adjusted with NaOH to make the solution acidic, and yellow sodium ferroaluminate is obtained by filtration. NH4HCO3 is added to the filtrate from which iron is removed, and CoCO3 is obtained by precipitation and filtration;

[0011] S4, separation and purification of Dy: the rare earth sodium sulfate double salt precipitate in step S2 is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and then subjected to 2-ethylhexyl phosphate mono-2-ethylhexyl ester extraction, stripping, oxalic acid precipitation and roasting to obtain Dy2O3;

[0012] S5. Separation and purification of Nd and Pr: The 2-ethylhexyl phosphate raffinate in step S4 is subjected to 2-ethylhexyl phosphate 2-ethylhexyl ester extraction, back extraction, oxalic acid precipitation and roasting to obtain Nd2O3, and the 2-ethylhexyl phosphate raffinate is subjected to oxalic acid precipitation and roasting to obtain Pr2O3.

[0013] Preferably, as an improvement, in step S1, the electrolyte is sulfuric acid and ferrous sulfate; the pH buffer is boric acid; Fe 2+ The complexing agent is one or more of ammonium sulfate, sodium citrate and ethylenediaminetetraacetic acid.

[0014] Preferably, as an improvement, the constant voltage electrolysis process conditions in step S1 are: the electrolyte pH value is 0-1.5, the initial Fe 2+ The concentration is 0.4-1.6mol / L and the voltage is 0.4-1.2V.

[0015] Preferably, as an improvement, in step S2, sodium sulfate is added to the electrolyte, the pH value of the solution is adjusted to be stable in the range of 1.4-1.8, and the sodium sulfate double salt precipitate of rare earth and the filtrate are obtained by filtering.

[0016] Preferably, in step S2, the pH value of the solution is adjusted to 1.6.

[0017] Preferably, as an improvement, the process conditions for recovering yellow sodium ferroalcohol in step S3 are: pH 1.8-2.5, the amount of H2O2 added is: H2O2 10-100 g / L, and the reaction temperature is 60-95°C.

[0018] Preferably, as an improvement, the process conditions for recovering CoCO3 in step S3 are: pH 6.5-7.5, NH4HCO3 concentration / Co 2+ The concentration is 1.5-2.0, and the reaction temperature is 20-90℃.

[0019] Preferably, the process conditions for recovering yellow sodium ferroaluminate in step S3 are: pH value is 1.9, H2O2 addition amount is: H2O2 40g / L, reaction temperature is 90°C; the process conditions for recovering CoCO3 are: pH value is 7.0, NH4HCO3 concentration / Co 2+ The concentration is 1.8 and the reaction temperature is 80°C.

[0020] Preferably, as an improvement, the conditions for extracting and separating Dy with the extractant 2-ethylhexyl phosphate in step S4 are: the organic phase comprises 10-50 vol.% of 2-ethylhexyl phosphate and 50-90 vol.% of sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 0.5:1-8:1, the extraction time is 5-30 min, and the extraction level is 1-20; the stripping conditions are: the HCl concentration is 0.1-6 mol / L, the volume ratio of the aqueous phase to the organic phase is 1:1-5:1, and the extraction level is 1-8.

[0021] Preferably, as an improvement, the conditions for extracting and separating Nd with the extractant 2-ethylhexyl phosphate 2-ethylhexyl ester in step S5 are: the organic phase comprises 10-40 vol.% of 2-ethylhexyl phosphate 2-ethylhexyl ester and 60-90 vol.% of sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 0.5:1-8:1, the extraction time is 5-30 min, and the extraction level is 1-20; the stripping conditions are: the HCl concentration is 0.1-6 mol / L, the volume ratio of the aqueous phase to the organic phase is 1:1-5:1, and the extraction level is 1-8.

[0022] Beneficial effects of this program:

[0023] (1) The present invention avoids energy-intensive process steps such as demagnetization, crushing and grinding, reduces energy consumption and shortens the recovery cycle.

[0024] (2) Ammonium sulfate, sodium citrate, and ethylenediaminetetraacetic acid were added as Fe during the electrolysis process. 2+ Complexing agent, which can inhibit Fe 2+ Fe 3+ The occurrence of side reactions can be reduced. In addition, by adding boric acid as a pH buffer and controlling the pH at 0-1.5, the formation of Fe(OH)3 can be avoided as much as possible, the adsorption of rare earths can be reduced, and the loss of rare earth elements can be reduced.

[0025] (3) First, separate the rare earth by double salt precipitation and then remove the iron, which is beneficial to avoid the iron precipitate adsorbing the rare earth and reducing the loss of rare earth. In addition, after the double salt precipitation, the residual Fe 2+ Fully oxidized to Fe 3+ Then, NaOH is used to increase the pH to generate sodium ferroaluminate [NaFe3(SO4)2(OH)6] precipitate, which is easier to filter than Fe(OH)3. The chemical reaction equation is as follows:

[0026] 2Fe 2+ +H2O2+2H + =2Fe 3+ +2H2O

[0027] 3Fe3+ +Na + +2SO4 2- +6H2O=NaFe3(SO4)2(OH)6↓+6H + .

[0028] (4) The present invention uses 2-ethylhexyl phosphate mono-2-ethylhexyl ester and 2-ethylhexyl phosphate 2-ethylhexyl ester to selectively extract and separate Dy, Nd and Pr, with a high separation coefficient, thereby improving the direct recovery rate of rare earth elements.

[0029] (5) The present invention comprehensively recovers all valuable metals in NdFeB alloy waste, including cobalt carbonate with a purity of more than 90%, through reasonable process design, and the prepared sodium ferroaluminate can be used as a high-efficiency water purifier, with high economic benefits.

[0030] In summary, the present invention has the characteristics of simple process, high metal purity, low material and energy consumption, and no pollution, and is conducive to large-scale industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the process of Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The following is further described in detail through specific implementation methods:

[0033] Embodiment 1:

[0034] A method for separating high-purity metal from NdFeB alloy waste, as shown in the following Figure 1 As shown, the following steps are included:

[0035] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 0.5, initial Fe 2+ The concentration is 1.0 mol / L and the voltage is 0.8 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0036] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.6, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0037] S3: Add 40g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 1.9, the reaction temperature is 90℃, and after reacting for 1.5h, filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 7.0, add NH4HCO3 solution, and the concentration of NH4HCO3 / Co 2+ Concentration = 1.8, after reacting at 80°C for 1 hour, high-purity CoCO3 was obtained by filtration.

[0038] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 10 vol.% P507 (2-ethylhexyl phosphate mono-2-ethylhexyl ester) and 90 vol.% sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 1:1, each extraction is 10 minutes, and after 10 levels of extraction, 1.5 mol / L HCl is used for back extraction, the volume ratio of the aqueous phase to the organic phase is 2:1, and 6 levels of extraction are performed. The back extract is precipitated with oxalic acid and roasted to obtain Dy2O3 with a purity of more than 99%.

[0039] S5: Add 20 vol.% PC-88A (2-ethylhexyl phosphate 2-ethylhexyl ester) and 80 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd, the volume ratio of organic phase to water phase is 2:1, each extraction is 15 minutes, after 6-stage extraction, use 3 mol / L HCl for back extraction, the volume ratio of water phase to organic phase is 3:1, and 5-stage extraction is performed. After oxalic acid precipitation and roasting, the back extract liquid is Nd2O3 with a purity of more than 99%. After oxalic acid precipitation and roasting, the raffinate is Pr2O3 with a purity of more than 99%.

[0040] Among them: the direct recovery rate of Dy is 98.5%, the direct recovery rate of Nd is 99.1%, and the direct recovery rate of Pr is 98.6%.

[0041] Embodiment 2:

[0042] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0043] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 1.5, initial Fe 2+ The concentration is 0.4 mol / L and the voltage is 0.4 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0044] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.4, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0045] S3: Add 10g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 1.8, the reaction temperature is 60℃, react for 0.5h and filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 6.5, add NH4HCO3 solution, NH4HCO3 concentration / Co 2+ Concentration = 1.5, after reacting at 20°C for 0.5h, high-purity CoCO3 was obtained by filtration.

[0046] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 50 vol.% P507 and 50 vol.% sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 0.5:1, each extraction is 5 minutes, and after the first stage of extraction, 0.1 mol / L HCl is used for back extraction, the volume ratio of the aqueous phase to the organic phase is 1:1, and the first stage of extraction is performed. After the back extract is precipitated with oxalic acid and roasted, Dy2O3 with a purity of more than 99% is obtained.

[0047] S5: Add 10 vol.% PC-88A and 90 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd, the volume ratio of organic phase to water phase is 0.5:1, each extraction is 30 minutes, after 1 stage extraction, use 0.1 mol / L HCl for back extraction, the volume ratio of water phase to organic phase is 1:1, and 8 stages of extraction are performed. After oxalic acid precipitation and roasting, the back extract liquid is obtained to obtain Nd2O3 with a purity of more than 99%. After oxalic acid precipitation and roasting, the raffinate is obtained to obtain Pr2O3 with a purity of more than 99%.

[0048] Among them: the direct recovery rate of Dy is 93.8%, the direct recovery rate of Nd is 93.6%, and the direct recovery rate of Pr is 92.9%.

[0049] Embodiment 3:

[0050] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0051] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 1.0, initial Fe 2+ The concentration is 1.6 mol / L and the voltage is 1.2 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0052] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.8, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0053] S3: Add 100g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 2.5, the reaction temperature is 95℃, and after reacting for 2.5h, filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 7.5, add NH4HCO3 solution, and the concentration of NH4HCO3 / Co 2+ Concentration = 2.0, after reacting at 90°C for 2h, high-purity CoCO3 was obtained by filtration.

[0054] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 30 vol.% P507 and 70 vol.% sulfonated kerosene, the volume ratio of organic phase to water phase is 8:1, each extraction is 30 minutes, after 20 levels of extraction, 6 mol / L HCl is used for back extraction, the volume ratio of water phase to organic phase is 5:1, and 8 levels of extraction are performed. After the back extract is precipitated with oxalic acid and roasted, Dy2O3 with a purity of more than 99% is obtained.

[0055] S5: Add 40 vol.% PC-88A and 60 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd, the volume ratio of organic phase to water phase is 8:1, each extraction is 30 minutes, after 20 levels of extraction, use 6 mol / L HCl for back extraction, the volume ratio of water phase to organic phase is 5:1, and after 1 level of extraction. After oxalic acid precipitation and roasting, the back extract liquid can obtain Nd2O3 with a purity of more than 99%. After oxalic acid precipitation and roasting, the raffinate can obtain Pr2O3 with a purity of more than 99%.

[0056] Among them: the direct recovery rate of Dy is 99.7%, the direct recovery rate of Nd is 99.4%, and the direct recovery rate of Pr is 99.6%.

[0057] Embodiment 4:

[0058] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0059] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 0.1, initial Fe 2+ The concentration is 1.6 mol / L and the voltage is 0.8 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0060] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.4, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0061] S3: Add 55g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 2.2, the reaction temperature is 80℃, react for 0.5h and filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 7.0, add NH4HCO3 solution, NH4HCO3 concentration / Co 2+ Concentration = 1.8, after reacting at 55°C for 1.5h, high-purity CoCO3 was obtained by filtration.

[0062] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 30 vol.% P507 and 70 vol.% sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 4:1, and each extraction is 20 minutes. After 10 levels of extraction, 3 mol / L HCl is used for back extraction, the volume ratio of the aqueous phase to the organic phase is 3:1, and 4 levels of extraction are performed. The back extract is precipitated with oxalic acid and roasted to obtain Dy2O3 with a purity of more than 99%.

[0063] S5: Add 25 vol.% PC-88A and 75 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd. The volume ratio of the organic phase to the aqueous phase is 4:1. Each extraction lasts 20 minutes. After 10 levels of extraction, 4 mol / L HCl is used for back extraction. The volume ratio of the aqueous phase to the organic phase is 1:1. After 5 levels of extraction, the back extract is precipitated with oxalic acid and roasted to obtain Nd2O3 with a purity of more than 99%. The raffinate is precipitated with oxalic acid and roasted to obtain Pr2O3 with a purity of more than 99%.

[0064] Among them: the direct recovery rate of Dy is 98.7%, the direct recovery rate of Nd is 98.9%, and the direct recovery rate of Pr is 98.6%.

[0065] Embodiment 5:

[0066] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0067] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 1.0, initial Fe 2+ The concentration is 1.0 mol / L and the voltage is 1.2 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0068] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.6, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0069] S3: Add 40g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 1.8, the reaction temperature is 95℃, and after reacting for 1.5h, filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 6.5, add NH4HCO3 solution, and the concentration of NH4HCO3 / Co 2+ Concentration = 1.5, after reacting at 20°C for 1 hour, high-purity CoCO3 was obtained by filtration.

[0070] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 10 vol.% P507 and 90 vol.% sulfonated kerosene, the volume ratio of organic phase to water phase is 8:1, each extraction is 5 minutes, after 5 levels of extraction, 2 mol / L HCl is used for back extraction, the volume ratio of water phase to organic phase is 5:1, and 2 levels of extraction are performed. After the back extract is precipitated with oxalic acid and roasted, Dy2O3 with a purity of more than 99% is obtained.

[0071] S5: Add 20 vol.% PC-88A and 80 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd. The volume ratio of the organic phase to the aqueous phase is 1:1. Each extraction lasts 5 minutes. After 5 levels of extraction, 2 mol / L HCl is used for back extraction. The volume ratio of the aqueous phase to the organic phase is 5:1. After 3 levels of extraction, the back extract is precipitated with oxalic acid and roasted to obtain Nd2O3 with a purity of more than 99%. The raffinate is precipitated with oxalic acid and roasted to obtain Pr2O3 with a purity of more than 99%.

[0072] Among them: the direct recovery rate of Dy is 98.0%, the direct recovery rate of Nd is 97.8%, and the direct recovery rate of Pr is 96.9%.

[0073] Embodiment 6:

[0074] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0075] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 1.5, initial Fe 2+ The concentration is 0.4 mol / L and the voltage is 0.4 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0076] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.7, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0077] S3: Add 80g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 2.0, the reaction temperature is 60℃, and after reacting for 2.5h, filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 7.5, add NH4HCO3 solution, and the concentration of NH4HCO3 / Co 2+ Concentration = 2.0, after reacting at 55°C for 0.5h, high-purity CoCO3 was obtained by filtration.

[0078] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 40 vol.% P507 and 60 vol.% sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 2:1, each extraction is 10 minutes, and after 6 levels of extraction, 3 mol / L HCl is used for back extraction, the volume ratio of the aqueous phase to the organic phase is 2:1, and 4 levels of extraction are performed. The back extract is precipitated with oxalic acid and roasted to obtain Dy2O3 with a purity of more than 99%.

[0079] S5: Add 15 vol.% PC-88A and 85 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd. The volume ratio of the organic phase to the aqueous phase is 6:1. Each extraction lasts 5 minutes. After 20 levels of extraction, 4 mol / L HCl is used for back extraction. The volume ratio of the aqueous phase to the organic phase is 1:1. After 6 levels of extraction, the back extract is precipitated with oxalic acid and roasted to obtain Nd2O3 with a purity of more than 99%. The raffinate is precipitated with oxalic acid and roasted to obtain Pr2O3 with a purity of more than 99%.

[0080] Among them: the direct recovery rate of Dy is 99.3%, the direct recovery rate of Nd is 98.7%, and the direct recovery rate of Pr is 99.9%.

[0081] Embodiment 7:

[0082] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0083] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 0.5, initial Fe 2+ The concentration is 1.0 mol / L and the voltage is 1.0 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0084] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.5, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0085] S3: Add 60g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 2.5, the reaction temperature is 70℃, react for 0.8h and filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 7.0, add NH4HCO3 solution, NH4HCO3 concentration / Co 2+ Concentration = 1.6, after reacting at 40°C for 2.0h, high-purity CoCO3 was obtained by filtration.

[0086] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 20 vol.% P507 and 80 vol.% sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 4:1, each extraction is 30 minutes, and after 5-stage extraction, 4 mol / L HCl is used for back extraction, the volume ratio of the aqueous phase to the organic phase is 4:1, and 5-stage extraction is performed. After the back extract is precipitated with oxalic acid and roasted, Dy2O3 with a purity of more than 99% is obtained.

[0087] S5: Add 20 vol.% PC-88A and 80 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd, the volume ratio of organic phase to water phase is 2:1, each extraction is 25 minutes, after 15 levels of extraction, use 5 mol / L HCl for back extraction, the volume ratio of water phase to organic phase is 2:1, and 6 levels of extraction are performed. After oxalic acid precipitation and roasting, the back extract liquid is obtained to obtain Nd2O3 with a purity of more than 99%. After oxalic acid precipitation and roasting, the raffinate is obtained to obtain Pr2O3 with a purity of more than 99%.

[0088] Among them: the direct recovery rate of Dy is 96.9%, the direct recovery rate of Nd is 98.4%, and the direct recovery rate of Pr is 98.9%.

[0089] Embodiment 8:

[0090] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0091] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 0.1, initial Fe 2+ The concentration is 0.6 mol / L and the voltage is 0.8 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0092] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.4, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0093] S3: Add 70g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 1.8, the reaction temperature is 65℃, and after reacting for 2.0h, filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 6.5, add NH4HCO3 solution, and the concentration of NH4HCO3 / Co 2+ Concentration = 1.5, after reacting at 90°C for 1.0h, high-purity CoCO3 was obtained by filtration.

[0094] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 50 vol.% P507 and 50 vol.% sulfonated kerosene, the volume ratio of organic phase to water phase is 6:1, each extraction is 25 minutes, after 20 levels of extraction, 1 mol / L HCl is used for back extraction, the volume ratio of water phase to organic phase is 4:1, and 6 levels of extraction are performed. After the back extract is precipitated with oxalic acid and roasted, Dy2O3 with a purity of more than 99% is obtained.

[0095] S5: Add 10 vol.% PC-88A and 90 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd. The volume ratio of the organic phase to the aqueous phase is 6:1. Each extraction lasts 20 minutes. After 10 levels of extraction, 1 mol / L HCl is used for back extraction. The volume ratio of the aqueous phase to the organic phase is 2:1. After 8 levels of extraction, the back extract is precipitated with oxalic acid and roasted to obtain Nd2O3 with a purity of more than 99%. The raffinate is precipitated with oxalic acid and roasted to obtain Pr2O3 with a purity of more than 99%.

[0096] Among them: the direct recovery rate of Dy is 98.9%, the direct recovery rate of Nd is 97.8%, and the direct recovery rate of Pr is 99.3%.

[0097] Embodiment 9:

[0098] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0099] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 1.5, initial Fe 2+ The concentration is 1.2 mol / L and the voltage is 1.0 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0100] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.7, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0101] S3: Add 10g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 1.8, the reaction temperature is 50℃, and after reacting for 2.0h, filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 7.5, add NH4HCO3 solution, and the concentration of NH4HCO3 / Co 2+ Concentration = 1.6, after reacting at 30°C for 1.5h, high-purity CoCO3 was obtained by filtration.

[0102] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 40 vol.% P507 and 60 vol.% sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 1:1, each extraction is 20 minutes, and after 15 levels of extraction, 5 mol / L HCl is used for back extraction, the volume ratio of the aqueous phase to the organic phase is 2:1, and 2 levels of extraction are performed. The back extract is precipitated with oxalic acid and roasted to obtain Dy2O3 with a purity of more than 99%.

[0103] S5: Add 30 vol.% PC-88A and 70 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd. The volume ratio of the organic phase to the aqueous phase is 1:1. Each extraction lasts 15 minutes. After 5 levels of extraction, 4 mol / L HCl is used for back extraction. The volume ratio of the aqueous phase to the organic phase is 3:1. After 2 levels of extraction, the back extract is precipitated with oxalic acid and roasted to obtain Nd2O3 with a purity of more than 99%. The raffinate is precipitated with oxalic acid and roasted to obtain Pr2O3 with a purity of more than 99%.

[0104] Among them: the direct recovery rate of Dy is 96.8%, the direct recovery rate of Nd is 98.6%, and the direct recovery rate of Pr is 99.2%.

[0105] Embodiment 10:

[0106] A method for separating high-purity metal from NdFeB alloy waste comprises the following steps:

[0107] S1: NdFeB alloy scrap is used as anode, inert material is used as cathode, electrolyte is sulfuric acid and ferrous sulfate, boric acid, ammonium sulfate and sodium citrate are added to the electrolyte, pH of the electrolyte is controlled to be 0.5, initial Fe 2+ The concentration is 0.4 mol / L and the voltage is 1.2 V. High-purity cathode iron and electrolytic tail liquid are obtained by electrolysis.

[0108] S2: After the electrolysis is completed, sodium sulfate is added to the electrolyte to adjust the pH value to be stable at 1.8, and the sodium sulfate complex salt precipitate and filtrate of the rare earth are obtained by filtration.

[0109] S3: Add 30g / L H2O2 to the filtrate, add NaOH to adjust the pH value to 2.2, the reaction temperature is 70℃, react for 0.5h and filter to obtain yellow sodium ferroaluminate. Adjust the pH value of the filtrate after removing iron to 6.5, add NH4HCO3 solution, NH4HCO3 concentration / Co 2+ Concentration = 2.0, after reacting at 40°C for 2.0h, high-purity CoCO3 was obtained by filtration.

[0110] S4: The rare earth sodium sulfate double salt precipitate is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and Dy is selectively extracted and separated by using 20 vol.% P507 and 80 vol.% sulfonated kerosene, the volume ratio of organic phase to water phase is 6:1, each extraction is 15 minutes, after 10 levels of extraction, 4 mol / L HCl is used for back extraction, the volume ratio of water phase to organic phase is 2:1, and 5 levels of extraction are performed. After the back extract is precipitated with oxalic acid and roasted, Dy2O3 with a purity of more than 99% is obtained.

[0111] S5: Add 25 vol.% PC-88A and 75 vol.% sulfonated kerosene to the P507 raffinate to selectively extract and separate Nd. The volume ratio of the organic phase to the aqueous phase is 2:1. Each extraction lasts 15 minutes. After 20 levels of extraction, 5 mol / L HCl is used for back extraction. The volume ratio of the aqueous phase to the organic phase is 1:1. After 4 levels of extraction, the back extract is precipitated with oxalic acid and roasted to obtain Nd2O3 with a purity of more than 99%. The raffinate is precipitated with oxalic acid and roasted to obtain Pr2O3 with a purity of more than 99%.

[0112] Among them: the direct recovery rate of Dy is 99.6%, the direct recovery rate of Nd is 99.7%, and the direct recovery rate of Pr is 98.9%.

[0113] The preparation processes of the above embodiments are the same, only the reaction conditions are different. It can be seen from the above embodiments that

[0114] The present invention directly uses NdFeB alloy waste as the anode for electrolysis, avoiding energy-intensive processes such as demagnetization, crushing and grinding. The comprehensive recovery of metals is achieved through electrolysis, extraction, precipitation, roasting and other processes. It has the characteristics of simple process, high metal purity, low material and energy consumption, and no pollution, and is easy to industrialize. Sulfonated kerosene is a commonly used extraction diluent. It is used in combination with the extractant to reduce the density of the extractant, reduce the viscosity, and increase the fluidity, thereby improving the physical properties of the extractant. Moreover, the prepared yellow sodium iron alum can be used in high-efficiency water purifiers, which has high economic benefits.

[0115] The above is only an embodiment of the present invention, and the common sense such as the known specific structure, characteristics and reactant ratio in the scheme is not described too much here. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, some deformations and improvements can also be made, such as simply adjusting the selection of parameters within or near the specified parameter range, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods in the specification and other records can be used to explain the content of the claims.

Claims

1. A method for separating high-purity metal from NdFeB alloy waste, characterized in that: The specific steps include: S1. Electrolysis: Use NdFeB alloy scrap as anode and inert material as cathode, add electrolyte, pH buffer, Fe 2+ The complexing agent is used to perform constant voltage electrolysis under acidic conditions to obtain electrolytic tail liquid and cathode iron; S2, double salt precipitation: adding sodium sulfate to the electrolytic tail liquid, adjusting the pH value of the solution to make the solution acidic, filtering to obtain sodium sulfate double salt precipitate and filtrate of rare earth; S3, separation of Fe and Co: H2O2 is added to the filtrate of step S2, the pH value of the solution is adjusted with NaOH to make the solution acidic, and yellow sodium ferroaluminate is obtained by filtration. NH4HCO3 is added to the filtrate from which iron is removed, and CoCO3 is obtained by precipitation and filtration; S4, separation and purification of Dy: the rare earth sodium sulfate double salt precipitate in step S2 is dissolved in hydrochloric acid to obtain a solution containing Dy, Nd and Pr, and then subjected to 2-ethylhexyl phosphate mono-2-ethylhexyl ester extraction, stripping, oxalic acid precipitation and roasting to obtain Dy2O3; S5. Separation and purification of Nd and Pr: The 2-ethylhexyl phosphate raffinate in step S4 is subjected to 2-ethylhexyl phosphate 2-ethylhexyl ester extraction, back extraction, oxalic acid precipitation and roasting to obtain Nd2O3, and the 2-ethylhexyl phosphate raffinate is subjected to oxalic acid precipitation and roasting to obtain Pr2O3.

2. The method for separating high-purity metal from NdFeB alloy waste according to claim 1, characterized in that: In step S1, the electrolyte is sulfuric acid and ferrous sulfate; the pH buffer is boric acid; Fe 2+ The complexing agent is one or more of ammonium sulfate, sodium citrate and ethylenediaminetetraacetic acid.

3. The method for separating high-purity metal from NdFeB alloy waste according to claim 1, characterized in that: The constant voltage electrolysis process conditions in step S1 are: the electrolyte pH value is 0-1.5, the initial Fe 2+ The concentration is 0.4-1.6mol / L and the voltage is 0.4-1.2V.

4. The method for separating high-purity metal from NdFeB alloy waste according to claim 1, characterized in that: In step S2, sodium sulfate is added to the electrolyte to adjust the pH value of the solution to be stable within the range of 1.4-1.8, and the sodium sulfate double salt precipitate of rare earth and the filtrate are obtained by filtration.

5. The method for separating high-purity metal from NdFeB alloy waste according to claim 4, characterized in that: In the step S2, the pH value of the solution is adjusted to 1.

6.

6. The method for separating high-purity metal from NdFeB alloy waste according to claim 1, characterized in that: The process conditions for recovering yellow sodium ferroalcohol in step S3 are: pH value is 1.8-2.5, H2O2 addition amount is: H2O2 10-100g / L, reaction temperature is 60-95°C, reaction time is 0.5-2.5h; the process conditions for recovering CoCO3 are: pH value is 6.5-7.5, NH4HCO3 concentration / Co 2+ The concentration is 1.5-2.0, the reaction temperature is 20-90°C, and the reaction time is 0.5-2h.

7. The method for separating high-purity metal from NdFeB alloy waste according to claim 6, characterized in that: The process conditions for recovering yellow sodium ferroalcohol in step S3 are: pH value is 1.9, H2O2 addition amount is: H2O2 40g / L, reaction temperature is 90°C, and reaction time is 1.5h; the process conditions for recovering CoCO3 are: pH value is 7.0, NH4HCO3 concentration / Co 2+ The concentration is 1.8, the reaction temperature is 80°C, and the reaction time is 1h.

8. The method for separating high-purity metal from NdFeB alloy waste according to claim 1, characterized in that: The conditions for extracting and separating Dy with the extractant 2-ethylhexyl phosphate in step S4 are: the organic phase includes 10-50 vol.% of 2-ethylhexyl phosphate and 50-90 vol.% of sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 0.5:1-8:1, the extraction time is 5-30 min, and the extraction level is 1-20; the stripping conditions are: the HCl concentration is 0.1-6 mol / L, the volume ratio of the aqueous phase to the organic phase is 1:1-5:1, and the extraction level is 1-8.

9. The method for separating high-purity metal from NdFeB alloy waste according to claim 1, characterized in that: The conditions for extracting and separating Nd with the extractant 2-ethylhexyl phosphate in step S5 are: the organic phase comprises 10-40 vol.% of 2-ethylhexyl phosphate and 60-90 vol.% of sulfonated kerosene, the volume ratio of the organic phase to the aqueous phase is 0.5:1-8:1, the extraction time is 5-30 min, and the extraction level is 1-20; the stripping conditions are: the HCl concentration is 0.1-6 mol / L, the volume ratio of the aqueous phase to the organic phase is 1:1-5:1, and the extraction level is 1-8.

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